Gouache paint consists of ground powdered pigments suspended in a water-soluble binder; it’s the opaque version of watercolour paint. Not unlike watercolours, gouache paint is a combination of pigment, gum arabic (binder), various plasticizers, and preservatives. The opacity in gouache is achieved by adding chalk or white pigment. Gouache has a very matte finish and the appearance of tempera. Water is used during application and when it evaporates, the binder fixes the pigments to any surface suitable for watercolours.
Gouache is re-wettable and reworkable like watercolours; however, it dries much faster than watercolours. The main difference between gouache and watercolours is a wet-to-dry colour shift. There is usually a slight change in hue between the wet and dry stages. This may pose a challenge when it comes to colour matching. Gouache has the characteristics of both acrylics and watercolours. Like acrylics, it has good coverage and like watercolour, it is reworkable and can be used to depict minute details. For those reasons, gouache is preferred by commercial artist and illustrators for creating posters, illustrations, and comics.
Acrylic gouache, which has all the qualities of traditional gouache, uses acrylic polymer emulsion as a binder. That means it is water-resistant once dry; there is no bleeding or lifting when rewetted or layered.